One very important piece of information that aircraft pilots must be aware of is the heading of the aircraft they are flying. In the United States, regulatory agencies quantify this need by requiring that the probability of a pilot losing all heading information is less than 10−9 per hour. The primary means for obtaining heading information in an airliner or large business jet is typically an inertial reference system (IRS) utilizing gyrocompassing and the rotation of the Earth to determine what direction an aircraft is heading. It is typical that an aircraft's inertial reference system employ 2 or 3 inertial reference units (IRUs) to provide a degree of redundancy to satisfy the 10−9 per hour regulation. One problem associate with redundancy is that a bank of identical IRUs would be susceptible to a common mode failure. That is, a latent defect present in each of the identical IRUs may cause them to all fail under the same conditions at the same time. To mitigate occurrences of a common mode failure that eliminates all heading information, a pilot is typically provided with at least one dissimilar source of heading information. Traditionally, a magnetic compass has been utilized by pilots to satisfy the need for a dissimilar source of heading information. However, modern aircraft are increasingly being controlled via electrical/electronic systems and devices that produce fields that interfere with the ability of magnetic sensors to measure the Earth's magnetic field. That is, the increasingly prevalent use of electronics on aircraft make it increasingly difficult to find a place on the aircraft where a magnetic sensor can be installed without interference from magnetic fields generated by other aircraft systems.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for improved systems and methods for providing aircraft heading information.